The fault tolerance theories of Arora and Kulkarni [3] and of Jhumka et al. [11] view a fault-tolerant program as the result of composing a fault-intolerant program with fault tolerance components called detectors and correctors. At their core, the theories assume that the correctness specifications under consideration are fusion closed. In general, fusion closure of specifications can be achieved by adding history variables to the program. However, addition of history variables causes an

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... ntial growth of the state space of the program, causing addition of fault tolerance to be expensive. To redress this problem, we present a method which can be used to add history information to a program in a way that (in a certain sense) minimizes the additional states. Hence, automated methods that add fault tolerance can now be efficiently applied in environments where specifications are not necessarily fusion closed.